This invention relates to a novel lead dioxide electrode excellent in shock-resistance, corrosion-resistance and electrical conductivity and free from electrodeposition strain.
Conventional lead dioxide electrodes are used as electrodes in the electrolytic oxidation for the manufacture of halogenates. Efforts are now being continued to develop applications for lead dioxide electrodes to be used as electrodes in the electrolytic treatment of waste water or as anodes in the diaphragm-process electrolysis of sodium chloride.
The manufacture of lead dioxide electrodes has heretofore been carried out by an acidic electrodeposition process which uses lead nitrate, for example, as the electrolyte. This process causes lead dioxide to be electrodeposited on the substrate. The lead dioxide layer consequently formed on the substrate consists preponderantly of .beta.-PbO.sub.2. The layer, therefore, inevitably suffers electrodeposition strain, entailing the disadvantage that the layer itself may develop cracks or may break when the formed layer is peeled off the substrate.
For the purpose of obtaining an electrode having fastness high enough to withstand the electrodeposition stress productive of internal strain, attempts have been made to improve the shape of the substrate, the composition of the electrolyte, and various other electrolytic conditions including use of additives. Perfect elimination of the electrodeposition strain from the .beta.-PbO.sub.2 layer obtained by the electrolysis in an acidic bath is impossible. The electrodes of the type formed of such layer, therefore, are deficient in shock-resistance and leave much to be desired from the practical point of view.
An object of the present invention is to provide a lead dioxide electrode which is practically free from electrodeposition strain and is excellent in electrical conductivity, corrosion-resistance, chemical-resistance and shock-resistance.
Another object of this invention is to provide a lead dioxide electrode the manufacture of which is very easy.